[FEAT] Add R PPA
[FEAT] Add R PPA

For installing R so that we can intall the `tm` package for working
through Drew Conway's book `Machine Learning for Hackers`.

Signed-off-by: Yan Han Pang <2a3dbd0474bc7e70adfd773b05f6c3249124ff3d@users.noreply.github.com>

yanhan/provision-ubuntu,yanhan/provision-ubuntu